Variable displacement vane pump

ABSTRACT

A variable displacement vane pump, including a pump body, a driving shaft, a rotor, a cam ring swingable on a swing support surface, first and second plate members on opposite sides of the cam ring, a suction port and a discharge port on a side of at least one of the first and second plate members, a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into first and second fluid pressure chambers, a fluid pressure control valve, a stop disposed on the pump body on a side of the first fluid pressure chamber and restricting a swing movement of the cam ring, and a detent disposed between the cam ring and the pump body on a side of the second fluid pressure chamber and preventing a rotational movement of the cam ring around the driving shaft.

BACKGROUND OF THE INVENTION

The present invention relates to a variable displacement vane pump which serves as a hydraulic power source of a hydraulic device such as a power steering apparatus for vehicles.

Japanese Patent Application First Publication No. 2002-168179 discloses a variable displacement vane pump which is applied to a power steering apparatus for vehicles. The variable displacement vane pump of the conventional art is so constructed as to cause change in volume of pump chambers by swinging a cam ring within a pump body and thereby control a flow rate of the working fluid discharged by the vane pump. The operation of the vane pump is controlled such that when the vane pump is operated at high speed, the flow rate of the working fluid discharged is decreased. First and second fluid pressure chambers are disposed outside the cam ring in a radially opposed relation to each other. The swing movement of the cam ring is controlled by fluid pressures which are introduced into the respective fluid pressure chambers. The cam ring is swingably moved on a support surface which is disposed within the pump body. A pin is disposed adjacent to the support surface in a circumferential direction of the cam ring and restrains a rotational movement of the cam ring within the pump body. A stop for limiting the swing movement of the cam ring is formed on a side of the first fluid pressure chamber within the pump body. With contact of the cam ring with the stop, the flow rate of the working fluid discharged becomes largest and an increased fluid pressure is applied to a discharge port of the vane pump. At this time, the increased fluid pressure is exerted on the cam ring which is supported by the stop and the support surface, from an inner circumferential side of the cam ring. An outer circumferential region of the cam ring extending between the portions at which the cam ring is contacted with the stop and the support surface is exposed to such a force as to induce a radial outward deformation thereof by the increased fluid pressure.

SUMMARY OF THE INVENTION

However, in the above-described conventional art, a recessed portion which is engaged with the pin is formed in the outer circumferential region of the cam ring extending between the portions at which the cam ring is contacted with the stop and the support surface. Therefore, the recessed portion undergoes stress concentration due to the increased fluid pressure. There might occur deterioration in durability of the cam ring and pump characteristics due to change in cam profile of the cam ring.

It is an object of the present invention to solve the above-described problem in the technologies of the conventional art and to provide a variable displacement vane pump which can suppress stress concentration in a cam ring and prevent deterioration in durability of the cam ring and pump characteristics due to change in cam profile of the cam ring.

In one aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor which is disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent disposed between the cam ring and the pump body on a side of the second fluid pressure chamber, the detent preventing a rotational movement of the cam ring around the driving shaft.

In a further aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent including a projection which is disposed on an outer circumferential surface of the cam ring, and a recessed portion which is disposed on an inner circumferential surface of the pump body on a side of the first fluid pressure chamber so as to be engaged with the projection, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the projection and the recessed portion.

In a still further aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent including a projection which is disposed on an end surface of the cam ring in an axial direction of the cam ring, and a recessed portion which is disposed on one of the first plate member and the second plate member so as to be engaged with the projection, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the projection and the recessed portion.

In a still further aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent including a first meshing portion which is disposed on an outer circumferential surface of the cam ring and a second meshing portion which is disposed on an inner circumferential surface of the pump body and always in meshing engagement with the first meshing portion, the first meshing portion and the second meshing portion being formed with a plurality of convexes and concaves, respectively, the detent preventing a rotational movement of the cam ring around the driving shaft by keeping the meshing engagement of the convexes and concaves of the first meshing portion and the convexes and concaves of the second meshing portion.

In a still further aspect of the present invention, there is provided a variable displacement vane pump, comprising:

a pump body;

a driving shaft supported on the pump body;

a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor,

a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor;

an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring;

a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively;

a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor;

a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port;

a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring;

a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and

a detent including a recessed portion which is disposed on an end surface of the cam ring in an axial direction of the cam ring and disposed on a side of the second fluid pressure chamber, and a projection which is disposed on one of the first plate member and the second plate member and engaged in the recessed portion, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the recessed portion and the projection.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a variable displacement vane pump of a first embodiment according to the present invention, taken in an axial direction of the variable displacement vane pump, namely, taken along line 1-1 of FIG. 2.

FIG. 2 is a cross-section of the variable displacement vane pump of the first embodiment, taken in a radial direction of the variable displacement vane pump, namely, taken along line 2-2 of FIG. 1, which shows the variable displacement vane pump placed in a maximum eccentric position.

FIG. 3 is an enlarged cross-section of the variable displacement vane pump of the first embodiment, which shows a detent.

FIG. 4 is a front view of a rear body of the variable displacement vane pump of the first embodiment.

FIG. 5 is an enlarged rear view of a pressure plate of the variable displacement vane pump of the first embodiment, which shows a pin holding hole formed in the pressure plate.

FIG. 6 is a diagram similar to FIG. 2 but omitting a rotor and vanes.

FIG. 7 is a cross-section of a second embodiment of the variable displacement vane pump, taken in a radial direction of the variable displacement vane pump.

FIG. 8 is a cross-section of a modification of the second embodiment of the variable displacement vane pump, taken in a radial direction of the variable displacement vane pump.

FIG. 9 is a cross-section of a further modification of the second embodiment of the variable displacement vane pump, taken in a radial direction of the variable displacement vane pump.

FIG. 10 is a cross-section of a third embodiment of the variable displacement vane pump, taken in a radial direction of the variable displacement vane pump.

FIG. 11 is a front view of a cam ring of the third embodiment of the variable displacement vane pump when viewed in a direction of axis x.

FIG. 12 is a side view of a cam ring of the third embodiment of the variable displacement vane pump when viewed in a direction of axis y.

FIG. 13 is a front view of a rear body of the third embodiment of the variable displacement vane pump when viewed in the direction of axis x.

FIG. 14 is a cross-section of a fourth embodiment of the variable displacement vane pump, taken in a radial direction of the variable displacement vane pump.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 through FIG. 6, a first embodiment of a variable displacement vane pump according to the present invention, is explained. In FIG. 1 through FIG. 6, arrows x, y and z denote directions of axes x, y and z, respectively, which extend perpendicular to each other. The direction of axis x is a direction of a central axis of driving shaft 2 of variable displacement vane pump 1 of the first embodiment. In order to facilitate understanding of the following explanation, a direction in which driving shaft 2 is inserted into front body 11 and rear body 12 is referred to as a positive direction of axis x. A direction in which spring 71 biases cam ring 4 of variable displacement vane pump 1, namely, a direction of a biasing force of spring 71, is referred to as a negative direction of axis y. A direction which extends toward suction passage IN is referred to as a positive direction of axis z.

FIG. 1 is a cross-section of variable displacement vane pump 1, taken in the axial direction, namely, taken along line 1-1 of FIG. 2. FIG. 2 is a cross-section of variable displacement vane pump 1, taken in the radial direction, namely, taken along line 2-2 of FIG. 1. In FIG. 2, cam ring 4 of variable displacement vane pump 1 is placed in a maximum eccentric position in the negative direction of axis y in which an eccentric amount of cam ring 4, namely, a displacement amount of cam ring 4, relative to driving shaft 2 is a maximum.

As shown in FIG. 1, variable displacement vane pump 1 includes driving shaft 2, rotor 3, cam ring 4, adapter ring 5 and pump body 10. Driving shaft 2 is supported on pump body 10 so as to be rotatable about the central axis. Driving shaft 2 is rotatably connected to an engine crankshaft, not shown, through a pulley, not shown.

Rotor 3 is disposed within an inside space of pump body 10 and rotatably driven by driving shaft 2 to make a unitary rotation with driving shaft 2. As shown in FIG. 2, a plurality of slots 31 are formed in an outer circumferential periphery of rotor 3 and circumferentially equidistantly spaced from each other. Each of slots 31 is formed as an axial groove which extends in an axial direction of rotor 3. Slot 31 also extends in a radial direction of rotor 3, in which vane 32 is disposed. Slot 31 is continuously connected with back pressure chamber 33 which is disposed at a radial-inner end of slot 31 and supplied with a working fluid. Vane 32 is movable out from slot 31 and into slot 31 in the radial direction of rotor 3 depending on change in fluid pressure of the working fluid within back pressure chamber 33.

As shown in FIG. 1, pump body 10 includes front body 11 and rear body 12 which are coupled with each other. Front body 11 is formed into a generally cup shape which has bottom 111 and an open end opened in the positive direction of axis x. Disk-shaped pressure plate 6 is disposed on bottom 111 of front body 11. Front body 11, pressure plate 6 and rear body 12 cooperate with each other to form pump element accommodating portion 112. Pump element accommodating portion 112 is disposed on an inner circumferential side of front body 11 and adjacent to pressure plate 6 in the positive direction of axis x. Rotor 3, cam ring 4 and adapter ring 5 are disposed within pump element accommodating portion 112.

Rear body 12 is fluid-tightly contacted with rotor 3, cam ring 4 and adapter ring 5 in a negative direction of axis x. Rotor 3, cam ring 4 and adapter ring 5 are supported by pressure plate 6 and rear body 12 from both the positive and negative directions of axis x.

Pressure plate 6 is formed with through-hole 66 into which driving shaft 2 is inserted. Suction port 62 and discharge port 63 are formed on end surface 61 of pressure plate 6 which is oriented in the positive direction of axis x. Suction port 121 and discharge port 122 are formed on front end surface 120 of rear body 12 which is oriented in the negative direction of axis x. Suction ports 62 and 121 are connected with suction passage IN for supplying the working fluid to a plurality of pump chambers B which are defined by rotor 3, vanes 32 and cam ring 4. Discharge ports 63 and 122 are connected with discharge outlet OUT for discharging the working fluid from pump chambers B.

As shown in FIG. 2, suction ports 62 and 121 are opened to suction region Bz+, whereas discharge ports 63 and 122 are opened to discharge region Bz−. In suction region Bz+, the volumes of pump chambers B are increased with the rotation of rotor 3. In discharge region Bz−, the volumes of pump chambers B are decreased with the rotation of rotor 3.

Adapter ring 5 is formed into a generally elliptic shape having a major axis which extends in the direction of axis y and a minor axis which extends in the direction of axis z. Adapter ring 5 is fitted to an inner circumferential periphery of front body 11. Adapter ring 5 serves as a part of front body 11 and forms an inner circumferential surface of front body 11. Adapter ring 5 has a generally elliptic bore in which cam ring 4 is disposed. Adapter ring 5 is restrained from rotating relative to front body 11 by pin 210 upon driving vane pump 1.

Cam ring 4 has an annular shape with substantially complete roundness and has an outer diameter which is substantially equal to a minor axis of the elliptic bore of adapter ring 5. Fluid pressure chamber A is formed between outer circumferential surface 42 of cam ring 4 and inner circumferential surface 53 of adapter ring 5. Cam ring 4 is swingably moveable within the elliptic bore of adapter ring 5 in the direction of axis y.

As shown in FIG. 2, seal 50 is disposed on an outer circumferential side of cam ring 4. Specifically, seal 50 is located in a most advanced position in the positive direction of axis z on inner circumferential surface 53 of adapter ring 5. On the other hand, swing support surface N is disposed in a most advanced position in a negative direction of axis z on inner circumferential surface 53 of adapter ring 5. Cam ring 4 is swingable about a swing fulcrum which is located on swing support surface N. Cam ring 4 is contacted with swing support surface N and swingably supported on swing support surface N in the negative direction of axis z.

Swing support surface N is formed by plate member 40 which is disposed on inner circumferential surface 53 of adapter ring 5. Seal 50 and swing support surface N cooperate with each other to divide a space on the outer circumferential side of cam ring 4, namely, fluid pressure chamber A, into first fluid pressure chamber A1 and second fluid pressure chamber A2. First fluid pressure chamber A1 is disposed in one swing direction of cam ring 4 in which cam ring 4 is swung to cause increase in a flow rate of the working fluid which is discharged from discharge port 63, 122. Second fluid pressure chamber A2 is disposed in the other swing direction of the cam ring in which cam ring 4 is swung to cause decrease in the flow rate of the working fluid which is discharged from discharge port 63, 122.

Stop 54 is disposed in a most advanced position on inner circumferential surface 53 of adapter ring 5 in the negative direction of axis y as shown in FIG. 2. Stop 54 comes into contact with cam ring 4 during the swing movement of cam ring 4 to thereby restrict the movement of cam ring 4 in the negative direction of axis y. Stop 54 has opposite end portions in the direction of axis x which are cut out and form communication groove 54 a. Communication groove 54 a allows fluid communication between one portion of first fluid pressure chamber A1 which is located in the positive direction of axis z and an opposite portion of first fluid pressure chamber A1 which is located in the negative direction of axis z.

Detent 200 is disposed between cam ring 4 and adapter ring 5 on a side of second fluid pressure chamber A2 and prevents a rotational movement of cam ring 4 around driving shaft 2. Detent 200 includes recessed portion 220 which is formed on outer circumferential surface 42 of cam ring 4, and pin 210 which is located between recessed portion 220 and adapter ring 5. As shown in FIG. 1, pin 210 extends into front body 11 and rear body 12 through pressure plate 6 in the direction of axis x. Pin 210 has opposite end portions which are inserted into front body 11 and rear body 12. Pin 210 and recessed portion 220 are engageable with each other to thereby prevent the rotational movement of cam ring 4 around driving shaft 2.

As shown in FIG. 1, front body 11 and rear body 12 are formed with pin holding holes 170 and 180 in which the opposite end portions of pin 210 are received and supported, respectively. Pressure plate 6 is formed with pin holding hole 65 which extends through pressure plate 6 in the direction of axis x. Pin 210 is inserted into pin holding holes 170, 180 and 65. Each of pin holding holes 170, 180 and 65 is configured to have an elliptic shape in cross-section as shown in FIG. 4 and FIG. 5.

With the elliptic configuration of pin holding holes 170, 180 and 65, pin 210 is displaceable in pin holding holes 170, 180 and 65. When a load is applied from cam ring 4 to pin 210, pin 210 is displaced and therefore can be prevented from undergoing deflection and deformation.

With the construction in which pin 210 extends through pressure plate 6 and is supported in pin holding holes 170 and 180 of front body 11 and rear body 12, the ability of pin 210 for supporting pressure plate 6 can be enhanced and the ability of detent 200 for restraining the rotational movement of cam ring 4 can be enhanced.

Seal 50 and swing support surface N are arranged in a substantially diametrically opposed relation to each other in a radial direction of cam ring 4. With this arrangement, even when there occurs a slight clearance between seal 50 and cam ring 4 due to the swing movement of cam ring 4, variation in the clearance can be reduced to thereby improve sealability of seal 50.

Rotor 3 has an outer diameter smaller than an inner diameter of cam ring 4. Rotor 3 is disposed within a central bore of cam ring 4 such that an outer circumferential surface of rotor 3 can be prevented from contacting with inner circumferential surface 41 of cam ring 4 even when cam ring 4 swings to cause change in the relative position of rotor 3 and cam ring 4 during the swing movement of cam ring 4.

When cam ring 4 is moved to the swing position farthest in the negative direction of axis y, a distance L between inner circumferential surface 41 of cam ring 4 and an outer circumferential surface of rotor 3 becomes maximum in the negative direction of axis y. When cam ring 4 is moved to the swing position farthest in the positive direction of axis y, the distance L becomes minimum in the positive direction of axis y.

Each of vanes 32 has a length in the radial direction of rotor 3 which is larger than the maximum value of the distance L. Vanes 32 can be always kept in contact with inner circumferential surface 41 of cam ring 4 while being received in slots 31 regardless of the relative position of cam ring 4 and rotor 3. Further, vanes 32 can be fluid-tightly contacted with inner circumferential surface 41 of cam ring 4 due to the fluid pressure which is always supplied from back pressure chamber 33.

Accordingly, a space between cam ring 4 and rotor 3 is divided into pump chambers B by vanes 32 which are disposed adjacent to each other in the circumferential direction of cam ring 4 and rotor 3. Pump chambers B are always kept fluid-tight and variable in volume with the rotation of rotor 3 when rotor 3 and cam ring 4 are positioned in the eccentric relation to each other.

Suction ports 62, 121 which are respectively formed in pressure plate 6 and rear body 12 are disposed along the outer circumference of rotor 3 as well as discharge ports 63, 122 which are respectively formed in pressure plate 6 and rear body 12. The supply and discharge of the working fluid through suction ports 62, 121 and discharge ports 63, 122 is performed due to variation in volume of pump chambers B.

Adapter ring 5 has radial through-hole 51 at an end portion thereof in the positive direction of axis y. Front body 11 has plug insertion hole 114 at an end portion thereof in the positive direction of axis y. Cup-shaped plug 70 which has one closed end is inserted into plug insertion hole 114 and serves to keep front body 11 and rear body 12 fluid-tight against an outside thereof.

Spring 71 is installed in an inside bore of plug 70 along an inner circumferential surface of plug 70 and expandable and compressible in the direction of axis y. Spring 71 extends into through-hole 51 and contacts and biases cam ring 4 in the negative direction of axis y. Spring 71 biases cam ring 4 in such a direction that an amount of the swing movement of cam ring 4 becomes maximum, thereby serving to stabilize the swing position of cam ring 4 at start-up of variable displacement vane pump 1 upon which the fluid pressure is unstable. That is, spring 71 serves to stabilize the flow rate of the working fluid to be discharged at start-up of variable displacement vane pump 1.

[Working Fluid Supply to First and Second Fluid Pressure Chambers]

As shown in FIG. 2, through-hole 52 is formed in adapter ring 5 in the positive direction of axis z and positioned apart from seal 50 in the negative direction of axis y. Through-hole 52 is opened to first fluid pressure chamber A1 at one end thereof. The other end of through-hole 52 is connected with fluid passage 113 which is formed in front body 11. Fluid passage 113 is opened to valve accommodating bore 115 which is formed in front body 11. Control valve 7 is disposed within valve accommodating bore 115 as well as valve spring 7 a which biases control valve 7 in the negative direction of axis y. Control valve 7 is communicated with first fluid pressure chamber A1 through fluid passage 113 and through-hole 52. The fluid pressure controlled by control valve 7 is introduced into first fluid pressure chamber A1 upon driving variable displacement vane pump 1.

Control valve 7 is connected with discharge ports 63, 122 via fluid passages 21, 22. Orifice 8 is provided in fluid passage 22. A downstream pressure on a downstream side of orifice 8 and an upstream pressure on an upstream side of orifice 8 as a discharge pressure which is discharged from discharge ports 63, 122 are introduced into control valve 7. Control valve 7 is driven by a differential pressure between the upstream pressure and the downstream pressure and a biasing force of valve spring 7 a and produces the controlled fluid pressure.

The controlled fluid pressure which is introduced into first fluid pressure chamber A1 is produced on the basis of the discharge pressure and a suction pressure which is sucked from suction ports 62, 121. The controlled fluid pressure is equal to or greater than the suction pressure.

On the other hand, the suction pressure is introduced into second fluid pressure chamber A2 via low fluid pressure supply passage 160 which is formed in rear body 12. Low fluid pressure supply passage 160 has one end connected with suction passage IN and the other end connected with suction port 121 via connection portion 161 which extends inwardly in the radial direction of cam ring 4. Low fluid pressure supply passage 160 is always opened to second fluid pressure chamber A2 regardless of the swing position of cam ring 4. Low fluid pressure supply passage 160 thus connects suction passage IN and second fluid pressure chamber A2 with each other.

That is, low fluid pressure supply passage 160 is disposed within an area on front end surface 120 of rear body 12 which is exposed to second fluid pressure chamber A2, and located between detent 200 and seal 50 near the side of seal 50 within the area. With this arrangement of low fluid pressure supply passage 160, introduction of the suction pressure into second fluid pressure chamber A2 can be facilitated.

Second fluid pressure chamber A2 always receives the suction pressure. Therefore, only fluid pressure P1 within first fluid pressure chamber A1 is controlled. In contrast, fluid pressure P2 within second fluid pressure chamber A2 is always kept equal to the suction pressure without being controlled. This allows fluid pressure P2 within second fluid pressure chamber A2 to be stabilized. As a result, disturbance of fluid pressure in vane pump 1 can be prevented so that stable control of the swing movement of cam ring 4 can be performed.

[Swing Movement of Cam Ring]

When the biasing force which is applied to cam ring 4 in the positive direction of axis y due to fluid pressure P1 within first fluid pressure chamber A1 becomes larger than a sum of the biasing forces which are applied to cam ring 4 in the negative direction of axis y due to fluid pressure P2 within second fluid pressure chamber A2 and spring 71, cam ring 4 is swung about the swing fulcrum on swing support surface N of plate member 40 in the positive direction of axis y. At this time, the volume of pump chamber By+ located in the positive direction of axis y is increased and the volume of pump chamber By− located in the negative direction of axis y is decreased.

When the volume of pump chamber By− is decreased, the flow rate of the working fluid which is supplied from suction ports 62, 121 to discharge ports 63, 122 is reduced so that the differential pressure between the upstream pressure on the upstream side of orifice 8 and the downstream pressure on the downstream side of orifice 8 is decreased. In response to the decrease in the differential pressure, control valve 7 is urged to move in the negative direction of axis y by valve spring 7 a so that the controlled fluid pressure is reduced. Therefore, fluid pressure P1 within first fluid pressure chamber A1 is decreased. When fluid pressure P1 within first fluid pressure chamber A1 becomes smaller than the sum of the biasing forces which are applied to cam ring 4 in the negative direction of axis y, cam ring 4 is swung in the negative direction of axis y.

When the biasing force which is applied to cam ring 4 in the positive direction of axis y and the sum of the biasing forces which are applied to cam ring 4 in the negative direction of axis y are substantially equal to each other and balanced, cam ring 4 is brought into and kept in a stationary state. At this time, the volume of pump chamber By+ is decreased and the volume of pump chamber By− is increased. The flow rate of the working fluid which is supplied from suction ports 62, 121 to discharge ports 63, 122 is increased so that the differential pressure between the upstream pressure on the upstream side of orifice 8 and the downstream pressure on the downstream side of orifice 8 is increased. In response to the increase in the differential pressure, control valve 7 is urged to move in the positive direction of axis y against the biasing force of valve spring 7 a so that the controlled fluid pressure is increased. Cam ring 4 is then swung in the positive direction of axis y. Actually, the eccentric amount of cam ring 4 is set such that the flow rate of the working fluid which is set on the basis of a diameter of orifice 8 and the spring force of valve spring 7 a can be constant and cannot cause hunting in the swing movement of cam ring 4.

[Detailed Construction of Detent]

FIG. 3 is an enlarged cross-section of a portion of variable displacement vane pump 1, which shows detent 200. FIG. 4 is a front view of rear body 12. FIG. 5 is a rear view of pressure plate 6 and shows pin holding hole 65. FIG. 6 is a partially enlarged diagram of FIG. 2, in which rotor 3 and vanes 32 are omitted.

Detent 200 includes pin 210, recessed portion 220 and pin holding groove 230. Recessed portion 220 and pin holding groove 230 are so disposed as to be opposed to pin 210 in a radial direction of pin 210 and prevent pin 210 from interfering with the swing movement of cam ring 4. Recessed portion 220 is formed on outer circumferential surface 42 of cam ring 4 and engageable with an outer circumferential surface of pin 210. Pin holding groove 230 is formed on inner circumferential surface 53 of adapter ring 5 and holds pin 210 with engagement with an outer circumferential surface of pin 210.

Pin 210 is disposed near plate member 40 to be slightly spaced therefrom in the positive direction of axis y. Specifically, pin 210 is located in an advanced position relative to plate member 40 in the positive direction of axis y. With this arrangement, when cam ring 4 is swung on swing support surface N of plate member 40, recessed portion 220 of cam ring 4 can be substantially prevented from being disengaged from pin 210. Therefore, this arrangement serves for reducing pin 210 in diameter. An angle which is formed by swing support surface N and a central axis of pin 210 may be set to 10 degrees or less.

Detent 200 is disposed on the side of second fluid pressure chamber A2. Since the suction pressure is introduced into second fluid pressure chamber A2, the suction pressure acts on both sides of pin 210 in the positive and negative directions of axis y, so that the fluid pressures on the both sides of pin 210 in the opposite directions of axis y are equal to each other. Therefore, the working fluid can be surely supplied to the side of pin 210 in the negative direction of axis y on which there is a relatively small radial clearance between cam ring 4 and adapter ring 5.

Pin 210 undergoes a uniform fluid pressure which acts on the circumferential surface of pin 210. Therefore, fluid pressure leakage from pin holding holes 170, 180 and 65 of front body 11, rear body 12 and pressure plate 6 can be suppressed as compared to the case where first and second fluid pressure chambers A1 and A2 are sealed from each other with pin 210. Since there occurs substantially no fluid pressure leakage, a supporting ability of pin 210 relative to pressure plate 6 can be enhanced regardless of pin holding hole 65 which penetrates through pressure plate 6.

Recessed portion 220 is so constructed as to generate a clearance between recessed portion 220 and pin 210 when cam ring 4 is swung in the negative direction of axis y and placed in the maximum eccentric position, namely, the most advanced position in the negative direction of axis y. With this construction, it is possible to ensure allowance for the movement of cam ring 4 and therefore suppress a load which is applied to cam ring 4.

Plate member 40 is made of a material which has a hardness higher than that of pump body 10, specifically, that of front body 11 and rear body 12. Plate member 40 having the higher hardness undergoes all the amount of radial load which is caused by the fluid pressure. This results in suppression of concentration of the load to pin 210. Plate member 40 is held in plate holding groove 55 which is formed on inner circumferential surface 53 of adapter ring 5.

Plate holding groove 55 is spaced from pin holding groove 230 which holds pin 210, in the circumferential direction of adapter ring 5. Thus, pin holding groove 230 and plate holding groove 55 are formed independently from each other. This serves for increasing accuracy in machining of pin holding groove 230 and therefore enhancing accuracy in positioning of pin 210.

[Function and Effect of the First Embodiment]

The functions and effects of the first embodiment are as follows.

In variable displacement vane pump 1 of the first embodiment, driving shaft 2 is supported on pump body 10. Rotor 3 is disposed within pump body 10 and rotatably driven by driving shaft 2. Rotor 3 is formed with a plurality of slots 31 which are spaced from each other in a circumferential direction of rotor 3. A plurality of vanes 32 are fitted into slots 31 so as to be moveable in a radial direction of rotor 3 and project from and retract into slots 31. Cam ring 4 is disposed within pump body 10 so as to be swingable on swing support surface N. Cam ring 4 cooperates with rotor 3 and vanes 32 to define a plurality of pump chambers B on an inner circumferential side of cam ring 4. Rear body 12 as a first plate member and pressure plate 6 as a second plate member are disposed on opposite sides of cam ring 4 in the axial direction of cam ring 4, respectively. Suction ports 62, 121 and discharge ports 63, 122 are disposed on a side of at least one of rear body 12 and pressure plate 6. Suction ports 62, 121 are opened to a suction region in which the volumes of pump chambers B are increased with the rotation of rotor 3. Discharge ports 63, 122 are opened to a discharge region in which the volumes of pump chambers B are decreased with the rotation of rotor 3. Seal 50 cooperates with swing support surface N to divide a space on an outer circumferential side of cam ring 4 into first fluid pressure chamber A1 and second fluid pressure chamber A2 which are disposed between seal 50 and swing support surface N. First fluid pressure chamber A1 is disposed in one swing direction of cam ring 4 in which cam ring 4 is swung to cause increase in a flow rate of a working fluid which is discharged from discharge ports 63, 122. Second fluid pressure chamber A2 is disposed in the other swing direction of cam ring 4 in which cam ring 4 is swung to cause decrease in the flow rate of the working fluid which is discharged from discharge ports 63, 122. Stop 54 is disposed on a side of first fluid pressure chamber A1 and restricts a swing movement of cam ring 4 in the one swing direction of cam ring 4. Control valve 7 controls a fluid pressure which is introduced into first fluid pressure chamber A1 or second fluid pressure chamber A2. Detent 200 is disposed between cam ring 4 and pump body 10 on a side of second fluid pressure chamber A2 and prevents a rotational movement of cam ring 4 around driving shaft 2.

A region which extends between stop 54 and swing support surface N in the circumferential direction of adapter ring 5 is located within the discharge region in which a large stress is exerted on cam ring 4 from the inner circumferential side of cam ring 4 due to the discharge pressure. Further, cam ring 4 has a reduced thickness in the radial direction at detent 200. Therefore, it is preferred that detent 200 is not arranged in the region between stop 54 and swing support surface N but arranged on a side of second fluid pressure chamber A2. With this arrangement, stress concentration to detent 200 of cam ring 4 can be avoided.

Detent 200 includes recessed portion 220 which is formed on outer circumferential surface 42 of cam ring 4, and pin 210 which is disposed between recessed portion 220 and front body 11 so as to be opposed to recessed portion 220. Pin 210 can prevent cam ring 4 from being rotated around driving shaft 2 with respect to front body 11.

Pressure plate 6 is disposed between front body 11 and cam ring 4 and biased toward cam ring 4 by the discharge pressure. Pressure plate 6 is formed with pin holding hole 65 which supports pin 210 and extends through pressure plate 6 in the direction of axis x. The fluid pressure which acts on pin holding hole 65 is the suction pressure, whereby there hardly occurs leakage of the fluid pressure from pin holding hole 65. With the provision of pin holding hole 65, the supporting ability of pin 210 relative to pressure plate 6 can be enhanced.

Front body 11 and rear body 12 are respectively formed with pin holding holes 170 and 180 which support the opposite end portions of support pin 210, respectively. With this construction, the supporting ability of pin 210 relative to pressure plate 6 can be further enhanced. In addition, the rotation preventing ability of pin 210 relative to the rotation of cam ring 4 around driving shaft 2 can be enhanced.

Pin holding holes 170 and 180 are formed into the elliptic shape which is elongated in the radial direction of pin 210. With this configuration, even when a load is applied from cam ring 4 to pin 210, pin 210 can be displaced or moved within pin holding holes 170 and 180 to thereby be free from suffering from deflection and deformation.

Pin 210 is disposed in the vicinity of swing support surface N. With this arrangement, when cam ring 4 is swung on swing support surface N, recessed portion 220 of cam ring 4 can be substantially prevented from being disengaged from pin 210. Therefore, it is possible to reduce pin 210 in diameter. The angle which is formed by swing support surface N and the central axis of pin 210 may be set to 10 degrees or less.

Low fluid pressure supply passage 160 which is opened to second fluid pressure chamber A2 and introduces the suction pressure into second fluid pressure chamber A2, is disposed between pin 210 and seal 50 near the side of seal 50. With this arrangement, introduction of the low pressure, namely, the suction pressure, into second fluid pressure chamber A2 can be facilitated.

Cam ring 4 is formed with recessed portion 220 on outer circumferential surface 42 which holds pin 210. Recessed portion 220 is so constructed as to generate a clearance between recessed portion 220 and pin 210 even when cam ring 4 is placed in the maximum eccentric position. With this construction, allowance for the movement of cam ring 4 can be ensured, serving for reducing a load which is applied to cam ring 4.

Control valve 7 controls the fluid pressure which is introduced into first fluid pressure chamber A1. Second fluid pressure chamber A2 receives at least the suction pressure. Therefore, the controlled fluid pressure may be introduced into both sides of pin 210 which are opposed to each other in the circumferential direction of cam ring 4. In this case, it is possible to suppress leakage of the controlled fluid pressure from pin holding hole 65 of pressure plate 6.

Detent 200 includes recessed portion 220 which is formed on outer circumferential surface 42 of cam ring 4, and pin 210 which is disposed between recessed portion 220 and adapter ring 5 so as to be engaged with recessed portion 220. Pin 210 can prevent the rotation of cam ring 4 relative to pump body 10 without interfering with the swing movement of cam ring 4.

Front body 11 further includes plate member 40 made of a material which has a hardness higher than that of front body 11 and rear body 12. With the provision of plate member 40 having the higher hardness, when plate member 40 undergoes the radial load which is caused due to the fluid pressure, pin 210 can be prevented from concentration of the load.

Pin 210 is held in pin holding groove 230 which is formed on the inner circumferential surface of front body 11, namely, inner circumferential surface 53 of adapter ring 5. Plate member 40 is held in plate holding groove 55 which is formed on the inner circumferential surface of front body 11, namely, inner circumferential surface 53 of adapter ring 5. Pin holding groove 230 and plate holding groove 55 are formed independently from each other to be spaced apart from each other in the circumferential direction of adapter ring 5. With this arrangement, it is possible to increase accuracy in machining of pin holding groove 230 and therefore enhance accuracy in positioning of pin 210.

Seal 50 and swing support surface N are arranged to be substantially diametrically opposed to each other in the radial direction of cam ring 4. With this arrangement, even when there occurs a slight clearance between seal 50 and cam ring 4 due to the swing movement of cam ring 4, variation in clearance can be minimized to thereby improve sealability of seal 50.

Referring to FIG. 7, there is shown a second embodiment of the variable displacement vane pump which differs from the first embodiment in construction of the detent. Like reference numerals denote like parts, and therefore, detailed explanations therefor are omitted. FIG. 7 is a cross-section of the variable displacement vane pump of the second embodiment, taken in the radial direction of cam ring 4. As shown in FIG. 7, detent 300 includes projection 310 which is disposed on outer circumferential surface 42 of cam ring 4, and recessed portion 320 which is disposed on inner circumferential surface 53 of adapter ring 5 so as to be opposed to projection 310. Recessed portion 320 is configured to be engageable with projection 310. Detent 300 prevents the rotational movement of cam ring 4 around driving shaft 2 with engagement of projection 310 and recessed portion 320. In this embodiment, pin 210 is used for holding pressure plate 6.

In the second embodiment, detent 300 is constituted of projection 310 which is disposed on outer circumferential surface 42 of cam ring 4, and recessed portion 320 which is disposed on inner circumferential surface 53 of adapter ring 5 as the inner circumferential surface of pump body 10 and opposed to projection 310. With this construction of detent 300, it is not necessary to form recessed portion 220 in cam ring 4 which is opposed to pin 210 as described in the first embodiment. Therefore, cam ring 4 without the recessed portion is free from reduction in cross-sectional area, so that the rigidity of cam ring 4 can be ensured. Further, projection 310 extends from outer circumferential surface 42 of cam ring 4 in the radial outward direction of cam ring 4 to thereby provide an enhanced rigidity at projection 310. Further, projection 310 is integrally formed with cam ring 4, whereby a separate part to be used as projection 310 is not necessary.

Referring to FIG. 8, there is shown a modification of the second embodiment of the variable displacement vane pump which differs from the second embodiment in construction of the detent. As shown in FIG. 8, plunger 80 is provided at an end of spring 71 which biases cam ring 4 in the negative direction of axis y. Plunger 80 has projection 310′ on a tip end portion thereof which is located in the negative direction of axis y. Recessed portion 320′ is disposed on outer circumferential surface 42 of cam ring 4 so as to be opposed to projection 310′. Recessed portion 320′ is configured to be engageable with projection 310′ and support projection 310′ such that cam ring 4 can be swung. Detent 300′ is constituted of projection 310′ and recessed portion 320′. Detent 300′ prevents the rotational movement of cam ring 4 around driving shaft 2 with engagement of projection 310′ and recessed portion 320′. Plunger 80 is biased by spring 71 to be moveable in the direction of axis y depending on the swing movement of cam ring 4.

In the modification of the second embodiment, plunger 80 is disposed on front body 11 so as to be opposed to outer circumferential surface 42 of cam ring 4 on the side of second fluid pressure chamber A2 and moveable in the radial direction of cam ring 4. Spring 71 biases plunger 80 toward cam ring 4. Detent includes the tip end portion of plunger 80 with projection 310′ and recessed portion 320′ which is disposed on outer circumferential surface 42 of cam ring 4 and supports projection 310′. With this construction, even when a swing angle of cam ring 4 is large, detent 300′ can surely prevent the rotational movement of cam ring 4 relative to pump body 10.

Referring to FIG. 9, there is shown a further modification of the second embodiment of the variable displacement vane pump which differs from the second embodiment in that the detent is disposed on a side of first fluid pressure chamber A1. As shown in FIG. 9, detent 300″ includes projection 310″ which is disposed on outer circumferential surface 42 of cam ring 4, and recessed portion 320″ which is disposed on inner circumferential surface 53 of adapter ring 5 on a side of first fluid pressure chamber A1 and engaged with projection 310″. Projection 310″ is integrally formed with cam ring 4. Recessed portion 320″ is located near swing support surface N and configured to be engageable with projection 310″. Detent 300″ prevents the rotational movement of cam ring 4 around driving shaft 2 with engagement of projection 310″ and recessed portion 320″. This modification can perform the same functions and effects of those of the second embodiment. Further, cam ring 4 is free from reduction in cross-sectional area which is caused due to formation of a recessed portion as a part of the detent. Therefore, cam ring 4 can be prevented from suffering from deterioration in rigidity to thereby ensure the rigidity of cam ring 4, regardless of the position of detent 300″ on the side of first fluid pressure chamber A1 in which a large stress is exerted on cam ring 4 from the inner circumferential side of cam ring 4 due to the discharge pressure.

Referring to FIG. 10 through FIG. 13, there is shown a third embodiment of the variable displacement vane pump which differs from the first embodiment in construction of the detent. FIG. 10 is a cross-section of the variable displacement vane pump of the third embodiment, taken in the radial direction of cam ring 4. However, for better understanding, FIG. 10 shows a front view of cam ring 4. FIG. 11 is a rear view of cam ring 4 when viewed in the direction of axis x. FIG. 12 is a side view of cam ring 4 when viewed in the direction of axis y. FIG. 13 is a front view of rear body 12 when viewed in the direction of axis x.

As shown in FIG. 12, cam ring 4 has projections 410 on axial end surfaces 43 thereof. Projections 410 extends in the axial direction of cam ring 4, namely, in the positive direction of axis x and the negative direction of axis x. One of projections 410 is shown in FIG. 11 and indicated by broken line in FIG. 10. As shown in FIG. 13, rear body 12 has recessed portion 420 on front surface 120. Recessed portion 420 is so disposed as to be engaged with one of projections 410 which is located on rear surface 43 of cam ring 4. Recessed portion 420 has a generally elliptic shape which extends in a circumferential direction of cam ring 4. The other of projections 410 is engaged in a recessed portion which is formed on a rear surface of pressure plate 6. The recessed portion of pressure plate 6 is formed into the generally elliptic shape like recessed portion 420 of rear body 12. With the elliptic configuration, projections 410 are moveable in recessed portion 420 of rear body 12 and the recessed portion of pressure plate 6 in the circumferential direction of cam ring 4. Therefore, cam ring 4 can be swung with the engagement of projections 410 and recessed portion 420. In this embodiment, pin 210 is used for holding pressure plate 6.

In the third embodiment, similar to the second embodiment, cam ring 4 is free from reduction in cross-sectional area which is caused due to formation of a recessed portion as a part of the detent. Cam ring 4, therefore, can be prevented from suffering from deterioration in rigidity to thereby ensure the rigidity of cam ring 4. Further, projections 410 are formed on axial end surfaces 43 of cam ring 4, so that an enhanced rigidity of projections 410 can be obtained. Further, since projections 410 are integrally formed with cam ring 4, it is not necessary to provide separate parts to be used as projections 410. Further, cam ring 4 can be formed with a through-hole extending through cam ring 4 in the axial direction of cam ring 4, and opposite end portions of a pin which is inserted into the through-hole can be used as projections 410. Projections 410 formed by the opposite end portions of the pin can also be enhanced in rigidity thereof.

Further, detent 400 may be constituted of projection 410 which is disposed on end surface 43 of cam ring 4 in the axial direction of cam ring 4, and recessed portion 420 which is disposed on one of rear body 12 and pressure plate 6 so as to be engaged with projection 410. Detent 400 prevents the rotational movement of cam ring 4 around driving shaft 2 with engagement of projection 410 of cam ring 4 and recessed portion 420 of rear body 12 or pressure plate 6. Further, detent 400 may be constituted of projection 410 which is disposed on one of rear body 12 and pressure plate 6, and recessed portion 420 which is disposed on end surface 43 of cam ring 4 in the axial direction of cam ring 4 so as to be engaged with projection 410. In these cases, the same functions and effects as described above can be obtained.

Referring to FIG. 14, there is shown a fourth embodiment of the variable displacement vane pump which differs from the first embodiment in construction of the detent. As shown in FIG. 14, detent 500 includes first meshing portion 510 disposed on outer circumferential surface 42 of cam ring 4 and second meshing portion 520 disposed on a surface of plate member 40 which forms a part of inner circumferential surface 53 of adapter ring 5. First meshing portion 510 and second meshing portion 520 are always in meshing engagement with each other. First meshing portion 510 and second meshing portion 520 have a gear shape formed by a plurality of convexes and concaves which are continuously arranged in the circumferential direction of cam ring 4 and adapter ring 5, respectively. Detent 500 prevents the rotational movement of cam ring 4 around driving shaft 2 by keeping the meshing engagement of the convexes and concaves of first meshing portion 510 and the convexes and concaves of second meshing portion 520. With this construction of detent 500, a load which is applied to detent 500 can be shared by the respective convexes and concaves of first meshing portion 510 and second meshing portion 520. As a result, cam ring 4 can be prevented from suffering from stress concentration.

In the fourth embodiment, detent 500 is constituted of first meshing portion 510 which is disposed on outer circumferential surface 42 of cam ring 4, and second meshing portion 520 which is disposed on the surface of plate member 40 as the inner circumferential surface of pump body 10 and always meshes with first meshing portion 510. The fourth embodiment can perform the same functions and effects as those of the first to third embodiments.

OTHER EMBODIMENT AND MODIFICATION

Detent which prevents the rotational movement of cam ring 4 around driving shaft 2 is not limited to the detents of the first to fourth embodiments and the modifications of these embodiments as explained above. Detent may include a recessed portion which is disposed on end surface 43 of cam ring 4 in the axial direction of cam ring 4 and disposed on a side of second fluid pressure chamber A2, and a projection which is disposed on one of rear body 12 as the first plate member and pressure plate 6 as the second plate member and engaged in the recessed portion of cam ring 4. The detent prevents the rotational movement of cam ring 4 around driving shaft 2 with engagement of the recessed portion of cam ring 4 and the projection of rear body 12 or pressure plate 6. The recessed portion of cam ring 4 may be a through-hole which extends through cam ring 4 in the axial direction of cam ring 4 and is engaged with the projection of rear body 12 or pressure plate 6. With the arrangement of the detent on the side of second fluid pressure chamber A2, the detent can be prevented from undergoing a large stress which is caused in the region between stop 54 and swing support surface N in the circumferential direction of cam ring 4. As a result, cam ring 4 can be prevented from suffering from stress concentration.

This application is based on a prior Japanese Patent Application No. 2007-077997 filed on Mar. 24, 2007. The entire contents of the Japanese Patent Application No. 2007-077997 are hereby incorporated by reference.

Although the invention has been described above by reference to certain embodiments of the invention and modifications of the embodiments, the invention is not limited to the embodiments and modifications described above. Further modifications and variations of the embodiments and modifications described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims. 

1. A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor which is disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor, a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively; a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor; a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port; a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring; a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and a detent disposed between the cam ring and the pump body on a side of the second fluid pressure chamber, the detent preventing a rotational movement of the cam ring around the driving shaft.
 2. The variable displacement vane pump as claimed in claim 1, wherein the detent comprises a recessed portion which is formed on an outer circumferential surface of the cam ring and a pin which is disposed between the recessed portion and the pump body so as to be engaged in the recessed portion.
 3. The variable displacement vane pump as claimed in claim 2, wherein the control valve controls the fluid pressure which is introduced into the first fluid pressure chamber, and the second fluid pressure chamber receives at least a suction pressure which is sucked from the suction port.
 4. The variable displacement vane pump as claimed in claim 3, wherein the second plate member is a pressure plate disposed between the pump body and the cam ring and biased toward the cam ring by a discharge pressure which is discharged from the discharge port, the pressure plate being formed with a pin holding hole which holds the pin and extends through the pressure plate in the axial direction of the cam ring.
 5. The variable displacement vane pump as claimed in claim 4, wherein the pump body is formed with a pin holding hole, the pin holding hole holding an axial end portion of the pin which penetrates through and projects from the pressure plate.
 6. The variable displacement vane pump as claimed in claim 5, wherein the pin holding hole of the pump body has an elliptic shape elongated in a radial direction of the pin.
 7. The variable displacement vane pump as claimed in claim 3, wherein the pin is disposed near the swing support surface.
 8. The variable displacement vane pump as claimed in claim 7, further comprising a low fluid pressure supply passage which is opened to the second fluid pressure chamber and introduces the suction pressure into the second fluid pressure chamber, the low fluid pressure supply passage being disposed on a side of the seal apart from the pin in a circumferential direction of the cam ring.
 9. The variable displacement vane pump as claimed in claim 2, wherein the cam ring comprises a pin holding groove which is formed on an outer circumferential surface of the cam ring and holds the pin, the pin holding groove being so arranged as to form a clearance between the pin holding groove and the pin when the cam ring is placed in a maximum eccentric position relative to the driving shaft in the one swing direction.
 10. The variable displacement vane pump as claimed in claim 1, wherein the control valve controls the fluid pressure to be introduced in the first fluid pressure chamber, and the second fluid pressure chamber receives at least a suction pressure which is sucked from the suction port.
 11. The variable displacement vane pump as claimed in claim 10, wherein the detent comprises a recessed portion which is formed on an outer circumferential surface of the cam ring, and a pin which is disposed between the recessed portion and the pump body so as to be engaged in the recessed portion.
 12. The variable displacement vane pump as claimed in claim 1, wherein the pump body comprises a plate member which forms the swing support surface, the plate member being made of a material which has a hardness higher than that of the pump body.
 13. The variable displacement vane pump as claimed in claim 12, wherein the detent comprises a pin holding groove which is formed on an inner circumferential surface of the pump body and a pin which is held in the pin holding groove, the plate member is held in a plate holding groove which is formed on the inner circumferential surface of the pump body, and the pin holding groove and the plate holding groove are spaced apart from each other in a circumferential direction of the pump body.
 14. The variable displacement vane pump as claimed in claim 1, wherein the seal and the swing support surface are disposed in substantially diametrically opposed relation to each other in a radial direction of the cam ring.
 15. The variable displacement vane pump as claimed in claim 1, wherein the detent comprises a projection which is disposed on an outer circumferential surface of the cam ring, and a recessed portion which is disposed on an inner circumferential surface of the pump body so as to be engaged with the projection.
 16. The variable displacement vane pump as claimed in claim 1, further comprising a plunger which is disposed on the pump body so as to be opposed to an outer circumferential surface of the cam ring on a side of the second fluid pressure chamber and moveable in a radial direction of the cam ring, and a biasing member which biases the plunger toward the cam ring, wherein the detent comprises a tip end portion of the plunger and a support portion which is disposed on the outer circumferential surface of the cam ring and supports the tip end portion of the plunger.
 17. A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor, a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively; a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor; a seal cooperating with the swing support surface to divide a space on an outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port; a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring; a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and a detent including a projection which is disposed on an outer circumferential surface of the cam ring, and a recessed portion which is disposed on an inner circumferential surface of the pump body on a side of the first fluid pressure chamber so as to be engaged with the projection, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the projection and the recessed portion.
 18. The variable displacement vane pump as claimed in claim 17, wherein the projection of the cam ring is integrally formed with the cam ring.
 19. A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor, a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively; a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor; a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port; a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring; a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and a detent including a projection which is disposed on an end surface of the cam ring in an axial direction of the cam ring, and a recessed portion which is disposed on one of the first plate member and the second plate member so as to be engaged with the projection, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the projection and the recessed portion.
 20. The variable displacement vane pump as claimed in claim 19, wherein the cam ring is formed with a through-hole which extends through the cam ring in an axial direction of the cam ring, and the projection of the cam ring is formed by an end portion of a pin that is inserted into the through-hole.
 21. The variable displacement vane pump as claimed in claim 19, wherein the projection of the cam ring is integrally formed with the cam ring.
 22. A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor, a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively; a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor; a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port; a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring; a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and a detent including a first meshing portion which is disposed on an outer circumferential surface of the cam ring and a second meshing portion which is disposed on an inner circumferential surface of the pump body and always in meshing engagement with the first meshing portion, the first meshing portion and the second meshing portion being formed with a plurality of convexes and concaves, respectively, the detent preventing a rotational movement of the cam ring around the driving shaft by keeping the meshing engagement of the convexes and concaves of the first meshing portion and the convexes and concaves of the second meshing portion.
 23. A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor being formed with a plurality of slots which are spaced from each other in a circumferential direction of the rotor, a plurality of vanes which are fitted into the slots so as to be moveable out from the slots and into the slots in a radial direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable on a swing support surface, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member which are disposed on opposite sides of the cam ring in an axial direction of the cam ring, respectively; a suction port and a discharge port which are disposed on a side of at least one of the first and second plate members, the suction port being opened to a suction region in which volumes of the pump chambers are increased with the rotation of the rotor, the discharge port being opened to a discharge region in which the volumes of the pump chambers are decreased with the rotation of the rotor; a seal cooperating with the swing support surface to divide a space on an outer circumferential side the cam ring into a first fluid pressure chamber and a second fluid pressure chamber which are disposed between the seal and the swing support surface, the first fluid pressure chamber being disposed in one swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being disposed in the other swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port; a stop disposed on the pump body on a side of the first fluid pressure chamber, the stop restricting a swing movement of the cam ring in the one swing direction of the cam ring; a control valve controlling a fluid pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber; and a detent including a recessed portion which is disposed on an end surface of the cam ring in an axial direction of the cam ring and disposed on a side of the second fluid pressure chamber, and a projection which is disposed on one of the first plate member and the second plate member and engaged in the recessed portion, the detent preventing a rotational movement of the cam ring around the driving shaft with engagement of the recessed portion and the projection. 